BRUSSELS (Reuters) - A Belgian teenager who blamed the local mayor for his father's suicide after he was fired from a town hall job has confessed to slashing the politician's throat in a cemetery on Monday night, public broadcaster RTBF said.

The murder of Alfred Gadenne, 71, the mayor of Mouscron and a former lawmaker in the regional parliament, has shocked the country, with the prime minister expressing his "horror".

The public prosecutor told Reuters that a man was under arrest after giving himself up to police at the scene after dark in Mouscron, an industrial border town of 57,000, close to the French city of Lille. He declined comment on media reports.

RTBF said the suspect was 18 and told police he was avenging his father, who killed himself two years ago after losing his job as a local council employee.

Gadenne, a conservative whose death prompted tributes from across the political spectrum, acted as caretaker for the cemetery next to his home and was killed after going there to lock up for the night, as he did every evening.

"I have learned with horror of the brutal death of Alfred Gadenne," Prime Minister Charles Michel said on Twitter. "All my thoughts are with his family and friends."